runtime(vim): Update base-syntax, remove unused vimString region
These were included with the initial release of the syntax file for Vim
5 and were probably intended to allow for syn-region start/skip/end
patterns with a '!' or '+' delimiter. However, these cases are
currently handled by the vimSynRegPat group.
The removed patterns never match anywhere in the distributed runtime
files and it is believed that this is generally true.
closes: vim/vim#140351633de8c35
Co-authored-by: Doug Kearns <dougkearns@gmail.com>
608f238bc6
